Thin film transistor array substrate and repairing method of the same

ABSTRACT

A thin film transistor (TFT) array substrate includes a substrate, a plurality of scan lines, a plurality of data lines, a plurality of thin film transistors, a plurality of pixel electrodes, and a plurality of pairs of repair pads is provided. A plurality of pixel regions are defined by the scan lines and the data lines over the substrate. The thin film transistors are disposed in the pixel regions and driven by the scan lines and the data lines. Each pixel electrode is disposed in the region, and is electrically connected to the thin film transistor. The repair pads are disposed under the data line. In addition, the repairing process includes welding the defective data line with the quasi-welding repair pad, and then forming a repair line to reconnect the defective data line.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 93102571, filed on Feb. 5, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a thin film transistor (TFT)array substrate and the repairing method thereof. More particularly, thepresent invention relates to a TFT array substrate and the repairingmethod thereof having high yield of repairing.

2. Description of Related Art

In recent years, the multimedia and the related devices are developedextensively due to the leaps and bonds of the semiconductor device orthe display device. As to the display device, the cathode ray tube (CRT)were broadly used in the past because of the good display quality andthe low price. However, the cathode ray tube has the disadvantages oflarge size, high power consumption and high environmental concerns.Since the liquid crystal display (LCD) has the advantages of lightweight, small size, thin thickness, low power consumption, low radiationand environmentally, the cathode ray tube is being gradually replaced bythe liquid crystal display. In general, the thin film transistor (TFT)LCD is most popularly applied in the LCD device.

Conventionally, the liquid crystal display (LCD) have dot defect or linedefect problems. In general, a dot defect is generated due to theabnormal electrical conduction between the top and bottom electrodes ofthe pixel capacitor by particle or defect. Moreover, the dot defect mayalso be generated due to the abnormal electrical conduction at theintersection of scan line and data line, thus, a white spot or a darkspot is formed in the intersection. Usually, a line defect is generatedby the breaking of scan line or data line. The yield of a liquid crystaldisplay (LCD) is quite dependent on the dot defect or line defect thattypically generate during the manufacturing of the LCD. Therefore, therepairing of the dot defect or line defect to further improve thedisplay quality is very important. Hereinafter, a conventional repairingtechnology will be described with reference to FIG. 1.

FIG. 1 is a drawing schematically illustrating the conventional laserchemical vapor deposition (CVD) repairing method. Referring to FIG. 1, aconventional pixel structure 100 includes at least a scan line 102, asignal line 104, a thin film transistor (TFT) 106 and a pixel electrode108. The thin film transistor (TFT) 106 includes a gate 106 a, a channellayer 106 b and a source/drain 106 c, in which the gate 106 iselectrically connected to the scan line 102, and the source/drain 106 care electrically connected to the signal line 104 and pixel electrode108 respectively.

Since the scan line 102 is a portion of the first metal layer M1, andthe signal line 104 is a portion of the second metal layer M2, the scanline 102 and the signal line 104 are electrically insulated from eachother by a first dielectric layer (or called gate isolation layer).Moreover, a second dielectric layer (or a protection layer) may beformed to cover the signal line 104. However, the intersection of thescan line 102 and the signal line 104 may be shorted abnormally due tothe faulty the dielectric layer, for example, due to contamination byimpurity or particles. Thereafter, repairing of the abnormally shortedintersection is required. A conventional repairing method is to cut bothends of the signal line 104 of the shorted intersection shown by thedotted line in FIG. 1. Then, two repairing openings 110 are formed byirradiating laser on the second dielectric layer. Thereafter, a repairline 112 is formed to reconnect the cut signal line 104 via the opening1 10 by performing a laser chemical vapor deposition (CVD) process.Therefore, the abnormally shorted intersection is repaired by aconventional method.

FIG. 2 is a cross-sectional view of the intersection repaired by aconventional laser repairing method. Referring to FIG. 2, it is notedthat the data line 104 may get damaged by laser beam when repairing inthe openings 110. Since a conventional data line 104 is usuallycomprised of molybdenum, aluminum and molybdenum multilayer metalstructure, and the melting point of aluminum is less than that of themolybdenum. Therefore, after the data line 104 laser is irradiated bythe laser beam to form the opening 110, the aluminum metal layer willget vaporized resulting in a formation of a data line with bent profileA as shown in FIG. 2. It is to be noted that, the repair line 112 formedby laser chemical vapor deposition (CVD) process may be susceptible tobreakage near the bent section at the bent profile A, and thus therepairing technique using laser CVD process is accordingly notdesirable.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a thin film transistor(TFT) array substrate capable of avoiding the open circuit of the repairline formed during the repairing process and thereby increase therepairing yield.

In addition, the present invention is also directed to a method ofrepairing a TFT array substrate capable of avoiding the open circuit ofthe repaired line formed during the repairing process and therebyincreasing the repairing yield.

In an embodiment of the present invention, the thin film transistor(TFT) array substrate, includes, for example but not limited to, asubstrate, a plurality of scan lines, a plurality of data lines, aplurality of thin film transistors, a plurality of pixel electrodes, anda plurality of repair pads. A plurality of pixel regions are defined bythe scan lines and the data lines disposed over the substrate. The thinfilm transistors are disposed in the pixel regions and driven by thescan lines and the data lines. Each pixel electrode is disposed in thepixel region and electrically connected to the thin film transistor. Therepair pads are disposed under the data lines.

In one embodiment of the invention, the TFT array substrate furtherincludes, for example but not limited to, a plurality of quasi-weldingrepair pads and at least a repair line. The quasi-welding repair padsare disposed under the data lines. The repair line crosses over at leasta defective scan line of the scan line. It is noted that, the defectivedata line includes, for example but not limited to, a defective linedisposed above the defective scan line and two normal lines disposed onboth sides of the defective scan line. The normal lines are welded tothe quasi-welding repair pads and mutually connected by the repair line.

In one embodiment of the invention, the quasi-welding repair pads areset in pairs. In another embodiment of the invention, the quasi-weldingrepair pads are set in pairs, and a partial portion of the quasi-weldingrepair pads are disposed under the data lines.

In one embodiment of the invention, the data line includes, for examplebut not limited to, a multilayer metal structure comprising a firstmetal layer, a second metal layer and a third metal layer. The meltingpoint of the first metal layer is higher than that of the second metallayer. Moreover, the data line includes, for example but not limited to,multilayer metal structure such as molybdenum, aluminum and molybdenumor other multilayer metal structure.

In one embodiment of the invention, the repair pad, for example, and thescan lines are comprised of same material. The repair pad, for example,is disposed under the data lines, or a portion of the repair pad isdisposed under the data lines.

In one embodiment of the invention, the pixel electrode is comprised of,for example but not limited to, indium tin oxide (ITO), indium zincoxide (IZO), indium-tin-zinc-oxide (ITZO) or other conductive material.

In one embodiment of the invention, the thin film transistor includes,for example but not limited to, a bottom gate amorphous silicon (a-Si)thin film transistor (TFT), a top gate a-Si TFT, a bottom gatepolysilicon thin film transistor (TFT), a top gate polysilicon thin filmtransistor (TFT), a bottom gate low temperature polysilicon thin filmtransistor (LTPS-TFT), or a top gate LTPS-TFT.

According to an embodiment of the present invention, a method ofrepairing the aforementioned thin film transistor (TFT) array substrateis provided. When at least a defective data line of the data lines andat least a defective scan line of the scan lines detected in the TFTarray substrate, the defective data line is cut to form a defective linedisposed above the defect scan line and two normal lines disposed onboth sides of the defective scan line. Thereafter, at least onequasi-welding repair pad corresponding to the defective data line andthe normal lines are welded. Then, at least one repair line is formed tocross over the defective scan line so as to connect with the normallines and the pair quasi-welding repair pad.

In one embodiment of the invention, the defective data line is cut by,for example but not limited to, using a laser cutting method. Further,the repair line is formed, for example but not limited to, by performinga laser chemical vapor deposition (CVD) process.

In one embodiment of the invention, in the step of welding thequasi-welding repair pad, the quasi-welding repair pads are set in pairsand located on two sides of an intersection of the scan line and thedata line respectively.

In one embodiment of the invention, in the step of welding thequasi-welding repair pad, the quasi-welding repair pads are set in pairsand located on two sides of an intersection of a common line and thedata line respectively.

In one embodiment of the invention, in the step of welding thequasi-welding repair pad, the quasi-welding repair pads are set in pairsand disposed under the data lines.

Accordingly, the present invention provides the repair pad disposedunder the data line. In addition, the repair pads are disposed on bothsides of the intersection of the scan line and the data line, ordisposed on both sides of the intersections of the common line and thedata line. Therefore, the defective data line (or normal line) that iscut could be welded to the corresponding pair of quasi-welding repairpads. Thereafter, the repair line is formed to complete the repair.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The following drawings illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 is a drawing schematically illustrating a conventional laserchemical vapor deposition (CVD) repairing method.

FIG. 2 is a cross-sectional view illustrating an intersection repairedby a conventional laser repairing method.

FIG. 3 is a drawing schematically illustrating a thin film transistorarray substrate according to one embodiment of the present invention.

FIG. 4 is a drawing schematically illustrating the TFT array substrateof FIG. 3 after being repaired by a laser repairing method.

FIG. 5 is a cross-sectional view schematically illustrating the TFTarray substrate of FIG. 4 taken along line A-A′.

FIG. 6A, FIG. 6B and FIG. 6C are views schematically illustrating thedistribution of repair pads and data lines with different sizesaccording to one embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a repaired portion afterthe normal line and the quasi-welding repair pads are welded accordingto one embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating the repaired portion afterthe laser repairing method is applied according to one embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

FIG. 3 is a drawing schematically illustrating a thin film transistorarray substrate according to one embodiment of the present invention.Referring to FIG. 3, the thin film transistor (TFT) array substrate 200comprises, for example but not limited to, a substrate 210 (shown inFIG. 5), a plurality of scan lines 220, a plurality of data lines 230, aplurality of thin film transistors 240, a plurality of pixel electrodes250, and a plurality pairs of repair pads 260. The scan lines 220 anddata lines 230 are formed over the substrate 210 to define a pluralityof pixel regions 212 over the substrate 210. The thin film transistors240 are disposed in each pixel region 212 respectively and driven by thecorresponding scan line 220 and data line 230. The pixel electrodes 250are also disposed in each pixel region 212 respectively and electricallyconnected to the corresponding thin film transistor 240. The repair padsof each pair of repair pads 260 are disposed at of the intersection ofeach scan line 220 and data line 230. Each pair of repair pads 260 isdisposed under the corresponding data line 230. Furthermore, the repairpads 260 are formed together with the gate of the thin film transistor240, thus the material of the repair pads 260 is, for example but notlimited to, the same as that of the scan line.

In one embodiment of the invention, the substrate 210 comprises, forexample but not limited to, glass, quartz, plastic, or other transparentinsulation substrate. The scan line 220 and the data line 230 arecomprised of, for example but not limited to, aluminum (Al), chromium(Cr), titanium (Ti), tungsten (W), tantalum (Ta), molybdenum (Mo), or amultilayer structure or alloys thereof. The thin film transistor 240includes, for example but not limited to, a bottom gate amorphoussilicon (a-Si) TFT, a bottom gate polysilicon TFT or a bottom gate lowtemperature polysilicon TFT (LTPS-TFT). The thin film transistor 240includes, for example but not limited to, a top gate a-Si TFT, a topgate polysilicon TFT or a top gate LTPS-TFT. A thin film transistor 240including the bottom gate a-Si TFT will be described in detail inreference with FIG. 3 according to one embodiment of the invention.

Referring to FIG. 3, the pixel electrode 250 comprises, for example butnot limited to, indium tin oxide (ITO), indium zinc oxide (IZO) or otherconductive transparent materials, or other conductive material withlight reflecting property such as metal. In other words, when the pixelelectrode 250 is comprised of transparent material, a transparent liquidcrystal panel may be constructed by combining the TFT array substrate200 with the other opposite aligned substrate. On the other hand, whenpixel electrode 250 is comprised of metal or other light reflectingmaterial, a reflective liquid crystal panel may be constructed when theTFT array substrate 200 is combined the other opposite alignedsubstrate. Moreover, when one portion of the pixel electrode 250 iscomprised of transparent material and the other portion thereof iscomprised of metal or other light reflecting material, asemi-transparent semi-reflective liquid crystal panel may be formedafter the TFT array substrate 200 and the other opposite alignedsubstrate are combined.

FIG. 4 is a drawing schematically illustrating the TFT array substrateof FIG. 3 after being repaired by a laser repairing method. FIG. 5 is across-sectional view schematically illustrating the TFT array substrateof FIG. 4 taken along line A-A′.

Referring to FIG. 4, when a defective scan line 220′ and a defectivedata line 230′ are abnormally conductive at the intersection of both,the data signal can not be written into the pixel controlled by thedefective scan line 220′ and the defective data line 230′. Therefore,the pixel needs to be repaired. In one embodiment of the presentinvention, the defective data line 230′ is cut to form a defective line232 and two normal lines 234, 236 at both sides of the defective scanlines 220′. The defective line 232 is above the defective scan line220′, and the normal lines 234 and 236 are at both sides of thedefective scan line 220′ respectively. In addition, the defective dataline 230′ is cut by using, for example but not limited to, a lasercutting method.

Thereafter, referring to FIG. 4 and FIG. 5, after the defective dataline 230′ is cut to form the defective line 232 and the normal lines 234and 236, a pair of quasi-welding repair pads 260′ corresponding to thedefective data line 230 are welded to the normal line 234 and 236respectively. It is noted that, the quasi-welding repair pads 260′ andthe normal lines 234 and 236 are welded by using, for example but notlimited to, a laser beam. The protection layer 280 above the normallines 234 and 236 are irradiated by the laser beam to form an opening282. Thereafter, the normal lines 234 and 236, the inter-gate dielectriclayer 270 and the quasi-welding repair pad 260′ are irradiated by thelaser beam, and then the inter-gate dielectric layer 270 will be burnedthrough to weld the normal lines 234 and 236 with correspondingquasi-welding repair pads 260′ respectively. The normal lines 234 and236 are electrically connected to the corresponding quasi-welding repairpads 260′ respectively by welding metal 285. In the embodiment, thewelding metal 285 is generated during the laser beam welding process,and gets deposited on, for example but not limited to, at least aportion of the sidewall of the opening 282.

Then, a repair line 290 crossing over the defective scan line 220′ isformed after the laser beam welding process to reconnect the normallines 234 and 236 that correspond to the quasi-welding repair pad 260′.In one embodiment, the repair line 290 is formed by performing, forexample but not limited to, a laser chemical vapor deposition (CVD)process.

Thereafter, the normal lines 234 and 236 of the defective data line 230′are welded to a portion of the quasi-welding repair pad 260′ after theTFT array substrate 200 is repaired and electrically connected to eachother by the repair line 290. Therefore, the defective line 232 of thedefective data line 230′ that is conducted to the defective scan line220′ will not adversely influence the driving of the pixel.

Thereafter, referring to FIG. 5, in one embodiment, the data line 230comprised of, for example but not limited to, a multilayer metalstructure such as a first metal layer 232, a second metal layer 234 andthird metal layer 236. In addition, the melting point of the first metallayer 232 is higher than that of the second metal layer 234. The firstmetal layer 232 and the third metal layer 236 is comprised of, forexample but not limited to, a molybdenum metal having a high meltingpoint. The second metal layer 234 is comprised of, for example but notlimited to, aluminum metal having a low melting point lower. Forexample, when the data line 230 is a multilayer metal structurecomprised of molybdenum, aluminum and molybdenum, if a conventionaldesign and repairing method is applied, the repairing process will fail.However, in the embodiment of the invention, the normal lines 234 and236 are welded to the quasi-welding repair pads 260′ and electricallyconnected to each other by repair line 290. Therefore, the forming andbreaking of the bending profile A near the repair line 112 as shown inFIG. 2 will not occur in the present invention. Thus, the repairingyield can be effectively increased.

FIG. 6A, FIG. 6B and FIG. 6C are views schematically illustrating thedistribution of repair pads and data lines with different sizesaccording to one embodiment of the present invention. Referring to FIG.6A to FIG. 6C, the size X of the repair pad 260 is, for example but notlimited to, less than the width W of the data line 230 (as shown in FIG.6A), equal to the width W of the data line 230 (as shown in FIG. 6B), orlarger than the width W of the data line 230 (as shown in FIG. 6C).Furthermore, the repair pad 260, for example but not limited to, neednot be totally disposed under the data line 230 (as shown in FIG. 6A),or a portion of the repair pad 260 is disposed under the data line 230(as shown in FIG. 6B and FIG. 6C). It is noted that, those skilled inthe art may change the shape, distribution, position, size and so on, ofthe repair pads 260, which is still within the scope and spirit of thepresent invention.

Referring to FIG. 6C, it is noted that in one embodiment of theinvention, the repair pads (or the quasi-welding repair pads) 260 areset in pairs and located on two sides of an intersection of the scanline and the data line 230 respectively.

In addition, referring to FIG. 6C, it is noted that in one embodiment ofthe invention, the repair pads (or the quasi-welding repair pads) 260are set in pairs and can also be located on two sides of an intersectionof a common line 222 and the data line 230 respectively. Thecharacteristic and function of the repair pad of the present embodimentis similar to the other embodiments described above and will not bedescribed in detail.

FIG. 7 is a cross-sectional view illustrating a repaired portion afterthe normal line and the quasi-welding repair pads are being weldedaccording to one embodiment of the present invention. FIG. 8 is across-sectional view illustrating the repaired portion after the laserrepairing method is applied according to one embodiment of the presentinvention. Referring to FIG. 7, after the normal line and thequasi-welding repair pads are welded, a repair line with a bent profilewill not generated at the welded surface thereof. Therefore, the repairline formed by the laser chemical vapor deposition (CVD) process willnot break easily.

Accordingly, the TFT array substrate and the method of repairing thereofis capable of providing a high repairing yield compared to that of theconventional technology. Furthermore, because the repair pad may beformed together with the gate of the thin film transistor, and thereforethis will not incur additional cost.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1-14. (canceled)
 15. A method of repairing the thin film transistor(TFT) array as claimed in claim 1 comprising at least a defective dataline and at least a defective scan line that conduct abnormally, themethod comprising: cutting the defective data line into a defective linedisposed above the defective scan line, and two normal lines, disposedon both sides of the defective scan line; welding at least onequasi-welding repair pad corresponding to the defective data line withthe normal lines; and forming at least one repair line crossing over thedefective scan line to connect the normal lines and the quasi-weldingrepair pad.
 16. The method of claim 15, wherein the step of cutting thedefective data line comprises a laser cutting method.
 17. The method ofclaim 15, wherein the step of forming the repair line comprisesperforming a laser chemical vapor deposition process.
 18. The method ofclaim 15, wherein in the step of welding the quasi-welding repair pad,the quasi-welding repair pads are set in pairs and located on two sidesof an intersection of the scan line and the data line respectively. 19.The method of claim 15, wherein in the step of welding the quasi-weldingrepair pad, the quasi-welding repair pads are set in pairs and locatedon two sides of an intersection of a common line and the data linerespectively.
 20. The method of claim 15, wherein in the step of weldingthe quasi-welding repair pad, the quasi-welding repair pads are set inpairs and disposed under the data lines.